A.

      B.

Figure 1. Stem density distributions by cycle in Hopewell Furnace National Historic Site (HOFU). Cycle 1: 2007 – 2010; Cycle 2: 2011 – 2014; Cycle 3: 2015 – 2018; Cycle 4: 2019 – 2023. Figure A shows regeneration densities by size class. Figure B shows tree density by diameter at breast height (DBH) increments. Error bars are 95% bootstrapped confidence intervals to account for non-normal error. An asterisk denotes a linear DBH distribution that is indicative of long-term recruitment failure.



Figure 2. Regeneration Debt status for the most recent 4-year census (2019 – 2023) in Hopewell Furnace National Historic Site (HOFU). Flat Tree Diam. Dist. stands for Flat Tree Diameter Distribution. If TRUE, the density of small trees is lower than expected due to chronic regeneration failure. Sapling/Seedling Composition is the % of total stems composed of native canopy-forming species. Sorenson is a measure of how closely the regen. layer matches canopy composition. For more details on metric calculations, thresholds and assessment of status, see Miller et al. 2023.


Figure 3. Deer browse impacts by cycle in Hopewell Furnace National Historic Site (HOFU). Cycle 1: 2007 – 2010; Cycle 2: 2011 – 2014; Cycle 3: 2015 – 2018; Cycle 4: 2019 – 2023.


Figure 4. Loess smoothed changes in stem density for seedlings (A) and saplings (B) by species group and sample year in Hopewell Furnace National Historic Site. Specified loess span approximated a linear trend between consecutive sample events per panel.



Figure 5. Loess smoothed changes in tree stem density (A) and basal area (B) by species group and sample year in Hopewell Furnace National Historic Site. Specified loess span approximated a linear trend between consecutive sample events per panel.



Figure 6. Loess smoothed changes in invasive plant percent cover by guild and sample year in Hopewell Furnace National Historic Site. Specified loess span approximated a linear trend between consecutive sample events per panel.



Table 1. Average plot-level seedling and sapling stem densities (stems per m2) and stocking index (at the 2m radius scale) by cycle. Only native, canopy-forming species are included. Note that Fraxinus spp. (ash species) are no longer considered canopy-forming species. Cycle 1: 2007 – 2010; Cycle 2: 2011 – 2014; Cycle 3: 2015 – 2018; Cycle 4: 2019 – 2023. Plots are sampled in 4-year rotations, with a quarter of the plots sampled each year (i.e. a panel). The stocking index quantifies whether current regeneration densities are sufficient to restock a forest canopy. The index is a weighted sum of seedling and sapling densities where larger seedling size classes get higher weights. Cells highlighted in green are plots that meet the minimum management target of 0.25 seedlings/m2 and 0.14 saplings/m2 or have a stocking index >100. These are the same thresholds used in Figure 2 and are described in Miller et al. 2023.

table output
Seedlings per sq.m
Saplings per sq.m
Stocking Index
Plot Panel Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 1 Cycle 2 Cycle 3 Cycle 4
50 1 0.17 0.00 0.25 0.00 0.11 0.09 0.06 0.05 3.14 0.00 25.38 0.00
51 1 1.75 1.17 1.00 0.75 0.00 0.00 0.02 0.04 25.13 39.84 71.38 104.93
52 1 0.83 0.25 0.75 0.92 0.09 0.09 0.08 0.07 10.43 3.14 9.42 11.56
53 1 0.17 0.08 0.25 0.08 0.00 0.00 0.00 0.00 2.14 1.01 3.14 1.01
83 2 0.00 0.00 0.08 0.08 0.00 0.00 0.00 0.00 0.00 0.00 1.01 1.01
84 2 0.17 0.75 1.08 0.08 0.01 0.01 0.01 0.01 2.14 10.43 17.84 2.14
85 2 0.75 1.75 1.42 1.33 0.00 0.00 0.00 0.00 11.56 30.41 21.99 21.99
86 2 0.67 0.75 1.83 2.83 0.04 0.04 0.06 0.45 24.25 28.40 61.07 279.98
163 3 0.25 0.25 0.17 0.42 0.00 0.00 0.00 0.00 3.14 4.15 2.14 6.28
164 3 2.00 8.58 9.33 6.50 0.00 0.00 0.00 0.26 30.41 206.34 486.95 563.85
165 3 0.25 0.08 0.17 0.25 0.00 0.00 0.00 0.00 3.14 1.01 2.14 3.14
166 3 0.00 0.00 0.00 0.08 0.01 0.01 0.01 0.01 0.00 0.00 0.00 1.01
247 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
248 4 0.50 0.58 1.00 0.33 0.02 0.01 0.01 0.00 7.29 10.43 13.57 4.15
249 4 0.00 0.58 1.00 0.58 0.00 0.00 0.00 0.00 0.00 7.29 16.71 9.42
251 4 0.00 0.50 0.58 0.25 0.04 0.00 0.00 0.07 7.41 10.43 82.69 99.90


Table 2. Average % cover and number of invasive species detected in each plot by cycle. Cycle 1: 2007 – 2010; Cycle 2: 2011 – 2014; Cycle 3: 2015 – 2018; Cycle 4: 2019 – 2023. Plots are sampled in 4-year rotations, with a quarter of the plots sampled each year (i.e. a panel). Plots with at least 10% average cover or 4 or more invasive species present are in yellow. Average cover and species counts may be increasing over time due to protocol changes, including additions to the indicator species list over time, a plot search for indicator species starting in 2009 and all woody species being sampled in quadrats starting in 2019. More details can be found in the MIDN Summary of Major Protocol Changes

table output
Average % Cover
Number of Species per Plot
PlotCode PanelCode Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 1 Cycle 2 Cycle 3 Cycle 4
50 1 70.00 41.59 102.03 87.51 1 6 8 8
51 1 11.46 6.58 22.06 28.19 5 6 6 7
52 1 0.00 0.00 0.00 0.00 0 0 0 1
53 1 79.83 67.81 97.34 95.33 2 5 5 7
83 2 46.02 40.98 6.18 26.11 4 8 8 10
84 2 8.95 4.33 5.47 12.67 4 5 5 8
85 2 0.01 0.13 0.16 21.74 1 3 3 6
86 2 0.00 0.00 0.00 2.53 0 1 1 6
163 3 1.22 11.35 2.22 5.68 6 6 7 8
164 3 0.00 0.45 0.65 1.77 3 6 5 6
165 3 22.29 44.62 37.39 44.69 7 7 7 9
166 3 4.38 39.27 51.12 49.16 1 3 3 4
247 4 85.71 94.00 81.79 93.94 8 8 8 8
248 4 58.99 89.85 40.25 53.92 5 5 4 6
249 4 31.98 70.96 14.64 12.47 6 6 6 6
251 4 0.01 10.12 6.18 5.68 3 4 6 8






Table 3. Number of plots out of 16 where priority invasive species were detected. Cycle 1: 2007 – 2010; Cycle 2: 2011 – 2014; Cycle 3: 2015 – 2018; Cycle 4: 2019 – 2023. Species on the list include all exotic vascular plant species that are capable of dominating Eastern US forest habitats, and does not include all exotic species detected in MIDN forest plots. Average cover and species counts may be increasing over time due to additions to the protocols, including a plot search for additional indicator species starting in 2009 and all woody species being sampled in quadrats starting in 2019. Species have also been added to the indicator list over time. More details can be found in the MIDN Summary of Major Protocol Changes

table output
Latin Name Common Name Cycle 1 Cycle 2 Cycle 3 Cycle 4
Ailanthus altissima Tree of heaven 0 0 1 0
Alliaria petiolata garlic mustard 5 2 3 3
Berberis thunbergii Japanese barberry 9 13 14 15
Berberis vulgaris common barberry 0 2 0 0
Celastrus orbiculatus oriental bittersweet 7 12 11 13
Euonymus burningbush 0 0 0 2
Euonymus fortunei climbing euonymus 1 0 0 0
Ligustrum privet 0 1 1 2
Lonicera - Exotic honeysuckle - exotic 2 2 2 5
Lonicera japonica Japanese honeysuckle 2 3 4 5
Microstegium vimineum Japanese stiltgrass 13 13 13 16
Persicaria longiseta Oriental lady's thumb 4 8 9 11
Persicaria perfoliata Asiatic tearthumb 0 0 2 8
Rosa multiflora multiflora rose 6 11 10 13
Rubus phoenicolasius wine raspberry 7 12 12 13
Viburnum dilatatum linden arrowwood 0 0 0 2



Table 4. Invasive plant and pest/pathogen early detections in Hopewell Furnace National Historic Site observed in the most recent census of each plot. Coordinates are in UTM NAD83 Zone 18N.

table output
Plot Year X Y Latin Name Common Name Type
HOFU-249 2023 434845 4451801 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-050 2019 435101 4451801 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-248 2023 434602 4452066 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-163 2022 434105 4450558 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-251 2023 435096 4451552 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-086 2022 435074 4452049 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-085 2022 434342 4452052 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-051 2019 434598 4449550 Persicaria perfoliata Asiatic tearthumb herbaceous
HOFU-083 2022 434359 4451310 Agrilus planipennis emerald ash borer pest